I would focus on the prevailing weather.

The southwest US has very good weather for flight training and a lot of flight schools. If you're training in the winter months, for example, somewhere warm like Phoenix would be very good; not so much in the summer.

Wherever you choose, a couple of tips.

1. Do not prepay for training. If a school insists that you prepay for the course, keep looking. You want to keep the flexibility to change schools if you aren't happy with your training. Also, there have been cases where schools go bankrupt while holding significant amounts of their student's prepaid funds. That doesn't mean that you can't prepay for blocks of hours in order to get a lower hourly rate. I wouldn't prepay for more than ten hours at a time, though, so as to limit your risk.

2. Just like in any other training, the student-instructor relationship is paramount. Every instructor isn't for every student. You need a good rapport with your instructor. Talk with several before you settle on you then don't be afraid to change if you later find that the rapport isn't there.